For now threads are using their Handle value as their Id, it should not really cause any problems because Handle values are unique in Citra, but it should be changed. I left a ToDo there because this is not correct behavior as per hardware.

All service calls in the CTR OS return result codes indicating the
success or failure of the call. Previous to this commit, Citra's HLE
emulation of services and the kernel universally either ignored errors
or returned dummy -1 error codes.

This commit makes an initial effort to provide an infrastructure for
error reporting and propagation which can be use going forward to make
HLE calls accurately return errors as the original system. A few parts
of the code have been updated to use the new system where applicable.

One part of this effort is the definition of the `ResultCode` type,
which provides facilities for constructing and parsing error codes in
the structured format used by the CTR.

The `ResultVal` type builds on `ResultCode` by providing a container for
values returned by function that can report errors. It enforces that
correct error checking will be done on function returns by preventing
the use of the return value if the function returned an error code.

Currently this change is mostly internal since errors are still
suppressed on the ARM<->HLE border, as a temporary compatibility hack.
As functionality is implemented and tested this hack can be eventually
removed.

This was automated using `clang-modernize`.

Most functions already operate on std::strings. This also removes the need to manually null terminate thread names.

Thread: Cleaned up arbitrate address functions.

Thread: Cleaned up ArbitrateAllThreads function.

Kernel: Made SyncRequest not pure virtual, with a default implementation of error (as this is not required for all kernel objects)

- SVC: Added ExitThread support
- SVC: Added SignalEvent support
- Thread: Added WAITTYPE_EVENT for waiting threads for event signals
- Thread: Added support for blocking on other threads to finish (e.g. Thread::Join)
- Thread: Added debug function for printing current threads ready for execution
- Thread: Removed hack/broken thread ready state code from Kernel::Reschedule
- Mutex: Moved WaitCurrentThread from SVC to Mutex::WaitSynchronization
- Event: Added support for blocking threads on event signalling

Kernel: Added missing algorithm #include for use of std::find on non-Windows platforms.

kernel: changed main thread priority to default, updated Kernel::Reschedule to use PrepareReschedule

thread: updated Reschedule to sit at a synchronization barrier when no other threads are ready for execution

thread: removed unused SwitchContext/Reschedule reason field, added missing arg parameter to SVC CreateThread

thread: moved ThreadStatus/WaitType to header, added support for arg on CreateThread, added correct CPSR reset

thread: added correct lowest thread priority, added a thread priority check, and added some comments